Gas turbines generally include a rotor with a number of circumferentially spaced buckets. The buckets generally include an airfoil, a platform, a shank, a dovetail, and other elements. The dovetail is positioned about the rotor and secured therein. The airfoils project into the gas path so as to convert the kinetic energy of the gas into rotational mechanical energy. During engine operation, vibrations may be introduced into the turbine buckets that can cause premature failure of the buckets if not adequately dissipated.
Many different forms of vibration dampers are known. One example is found in commonly owned U.S. Pat. No. 6,851,932, entitled “VIBRATION DAMPER ASSEMBLY FOR THE BUCKETS OF A TURBINE.” The dampers shown therein may be used in the 6C-stage 2 bucket as is offered by General Electric Company of Schenectady, N.Y. The 6C-stage 2 bucket may experience relatively high vibratory stresses during, for example, transient operations.
Although these known dampers may be largely adequate during typical operation, known designs have locked up on occasion due to higher than expected frictional forces. Known designs also were believed to be binding on the sharp edges of the buckets due to functional intolerances with respect to manufacturing variances in the contact surfaces. As such, there is a desire to improve overall damper effectiveness, provide tolerance of radial misalignment of adjacent bucket contact surfaces, provide a low susceptibility to friction lock up, ensure proper bucket contact, prohibit rotation of the damper during startups and shutdowns, and ensure proper installation of the damper. These goals preferably may be accommodated and achieved without loss of overall system efficiency.